Air in a room is contaminated with various substances such as dust, tobacco smoke, and carbon dioxide exhaled by respiration. Because modern houses are highly airtight, such contaminants tend to accumulate in a room, so that it is necessary to actively ventilate air in a room. However, for houses and offices in comparatively heavily air-polluted areas, it is not preferable to ventilate air through a window, because polluted air is undesirably taken into a room. For houses and the like in less air-polluted areas, pollen may be taken into a room depending on the season, which is not desirable for people suffering from hay fever.
Accordingly, air purifiers of types placed on a floor or a table are used to purify air without opening a window. A typical method of purifying air in a room is to suck in air, collect dust and the like using a filter, and absorb contaminants using activated carbon or the like. Therefore, air purifiers have the following basic structure.
An air passage in which a blower is disposed is formed in a body of an air purifier. An air inlet is disposed at the entrance of the air passage, and an air outlet is disposed at the exit of the air passage. A dust filter and a deodorizing filter are disposed in the air passage to remove dust, unpleasant odors, and the like. Moreover, an ion generating unit is disposed in the air passage, and ions generated by the ion generating unit are released into a room together with purified air. Airborne mold, bacteria, and the like in the room are inactivated as a result of being surrounded by the released ions. Thus, the air purifier purifies air in a room (see, for example, Japanese Unexamined Patent Application Publication No. 2000-121111).
Because apparatuses have been designed to provide a better low-noise performance, there are air purifiers having air inlets structured in various ways. The apparatus described in Japanese Unexamined Patent Application Publication No. 2000-121111 is a front-inlet-type apparatus having an air inlet in a front surface thereof.
However, in general use, air purifiers are placed on a floor surface near a wall while a user is present in a middle part of the room. Therefore, back-inlet-type apparatuses, which have an air inlet in a back surface thereof to reduce air intake noise of the blower heard by a user, are also marketed (see, for example, Japanese Unexamined Patent Application Publication No. 2009-085511).